1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image with toners of multiple colors and to an image forming apparatus control method.
2. Description of the Related Art
Conventionally, there is a known image forming apparatus that forms electrostatic latent images on photoreceptors through optical writing, temporarily transfers toner images developed from the electrostatic latent images onto an intermediate transfer member, such as an intermediate transfer belt, for each of colors such that the toner images of the respective colors are superimposed on the intermediate transfer member, transfers the toner images of the respective colors from the intermediate transfer member to a sheet of paper, and fixes the toner images to the sheet of paper to thereby form a color image.
In such an image forming apparatus, image adjustment, such as color misregistration correction or density correction, on an image to be formed is generally performed by forming a test pattern on the intermediate transfer belt and detecting the test pattern by a sensor. However, normal image formation on the sheet of paper cannot be performed while the above-described image adjustment is being performed. Therefore, if the image adjustment is frequently performed, downtime increases, during which the image formation on the sheet of paper is interrupted. Consequently, it becomes difficult to efficiently form images.
Japanese Patent Application Laid-open No. 2006-293240 discloses a technology in which, in an image forming apparatus where the maximum image width available for image formation in the main-scanning direction is smaller than a sum of the maximum width of an available recording material in the main-scanning direction and the lengths of pattern images formed at two portions for density correction or misregistration correction in the width direction of the recording material, an area where the pattern images are to be formed is changed depending on whether the width of a recording material to be actually used is equal to or smaller than a threshold or whether the width of the recording material is greater than the threshold. More specifically, if the width of a recording material to be used is equal to or smaller than the threshold, the pattern images are formed in an image area through which a sheet of paper does not pass, and, if the width of the recording material is greater than the threshold, the pattern images are formed in an inter-sheet area between the trailing end of a preceding recording material and the leading end of a following recording material. According to Japanese Patent Application Laid-open No. 2006-293240, it is possible to prevent an increase in the size of the image forming apparatus in the sheet width direction due to formation of the pattern images for density correction or misregistration correction in an area outside the maximum sheet width, and it is also possible to prevent a decrease in the throughput due to formation of the pattern images in the inter-sheet area.
Meanwhile, in the conventional image adjustment method in which a test pattern is formed in an area outside a printing area in parallel with printing of the image, an execution condition is set such that the size of a printing image in the main-scanning direction is smaller than a predetermined size in order to prevent overlapping of the printing image and the test pattern, but the size of the printing image in the sub-scanning direction is not set in the execution condition.
An example will be described below, in which images are sequentially formed on a page-by-page basis. In this case, an image formation condition for a next page following a current page is set after completion of the image formation of the current page is detected. When a test pattern is formed in parallel with the printing image, settings for the test pattern are set at the same time settings for the next page are set.
When the test pattern is formed in parallel with the printing image without taking into account the image size in the sub-scanning direction, a timing at which formation of the printing image is completed and a timing at which formation of the test pattern is completed cannot be distinguished. Therefore, in the conventional operation for setting image settings for a next page after detecting the completion of the image formation of a current page, the image settings may be set even before formation of the test pattern is not completed. In this case, there is a problem in that a formation condition for the test image may be changed while the test pattern is being formed.
In the technology disclosed in Japanese Patent Application Laid-open No. 2006-293240, because only a sheet size in the main-scanning direction is set as a determination condition, if the test pattern is formed without taking into account the image size in the sub-scanning direction, a timing of completion of the formation of the test pattern cannot be distinguished. Therefore, even with the technology of Japanese Patent Application Laid-open No. 2006-293240, it is difficult to set the image settings for a next page at an appropriate timing, so that it is difficult to solve the problem in that the formation condition for the test image may be changed while the test pattern is being formed.
Therefore, there is a need for an image forming apparatus capable of executing image settings at an appropriate timing when a test pattern is formed in an area outside a printing area in parallel with printing of the image.